Expansion personal computer (PC) buses operate in consumer, server, and industrial applications. These buses provide a PC motherboard-level interconnect (e.g., to link motherboard-mounted peripherals) that includes a passive backplane interconnect and an expansion card interface for add-in boards. In virtually all modern personal computers, from consumer laptops and desktops to enterprise data servers, the expansion bus serves as the primary motherboard-level interconnect, connecting the host system-processor with both integrated-peripherals (surface-mounted ICs) and add-on peripherals (expansion cards). In many of these systems, the expansion bus co-exists with one or more legacy buses, for backward compatibility with a large body of legacy peripherals.